(1) Field of the Invention
The present invention relates to the detection of acoustic signals. More specifically, the present invention relates to a sonar system which uses an array of acoustic vector sensors for detecting acoustic signals.
(2) Description of the Prior Art
The undersea operations of the Navy have shown a shift from deep water, open ocean environments to littoral, shallow water environments. These new environments often have high ambient noise levels and varying bottom conditions which reduce or impair the ability of existing sonar systems to detect, at a reasonable distance, all but low frequency acoustic signals. Thus, there is a need for an improved sonar system to detect acoustic signals in noisy, shallow water environments.
A fundamental measure of array performance is directivity. Increases in directivity can provide increased detection range and resolution. Conventional sonar systems use arrays of pressure sensors (hydrophones) to detect acoustic signals. For an array of pressure sensors, gains in directivity are fundamentally limited by the size of the array. Therefore, the only way to increase the directivity of an array of pressure sensors is to increase the size, or aperture, of the array.
In conventional submarine sonar arrays, the hydrophones are typically mounted to a steel conditioning plate or similar structure to enhance signal reception (pressure doubling). Increasing directivity by building a large aperture array would require heavy and unyielding signal conditioning plate. Creating a large aperture, low frequency array would require a relatively thick plate to create a rigid boundary condition. Such a large conditioning plate is unfeasible in many applications. Therefore, an improved sonar system, capable of detecting acoustic plane waves in noisy environments would be a welcome addition to the art.